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with 'INCOR' 24-Hour Ceirien 

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SATURDAY NOON: After close of business, the old floor is 
dug up and resurfacing begins. 'Incor' concrete is placed Satur- 
day night, job completed early Sunday morning. 

MONDAY S A.M. : New floor in use, no interruption to business, 
and 'Incor' concrete thoroughly cured. A better floor in a frac- 
tion of the usual time. 


PROMINENT builder recently said that "the floor is the only 
part of the structure that receives any wear — yet, it usually gets 
the least attention." Like most generalities, this one appears to 
have some basis in fact; for recent observation indicates that two 
out of every three industrial floors today need repair or complete 
resurfacing. In this book, emphasis is placed upon repairs to 
existing floors. However, the same methods are used in new con- 
struction, both monolithic and placed -afterward; the only essen- 
tial difference being in the preparation of the base. 

Copyrighted, 19J4, International Cement Corp. 


Heavy-Duty Floors 

How Heavy-Duty Floors are built and repaired . . . 
Thorough curing essential . . . Why 'Incor' Cement makes 
better floors, in a fraction of the usual time. 


Most industrial floors take a terrific beating; 
steel-tired trucks, acids and corrosives, as well as 
less aggressive agents are encountered. So, in addi- 
tion to adequate strength, a heavy-duty floor must 
also be dense and watertight. And that means 
good concrete. Unsound, slipshod methods which 
get by elsewhere, soon show up in a floor. 

Fortunately, the problem is simple, because the 
selection of materials and water content, as well as 
methods of mixing, placing and finishing are well 
standardized. Follow carefully and skilfully a few 
simple rules based on sound principles, and satis- 
factory results are readily obtained. 

The problem comes down to a question of ade- 
quate curing. Here a note of caution is important: 
For durability the floor must be thoroughly cured, 
—most floor failures are due to insuflRcient curing. 

To be dense, watertight and wear-resisting, con- 
crete made with ordinary Portland cement has to 
be kept wet lo days. The reader can answer from 
his own experience how many jobs get that much 
curing! As a matter of fact, it is usually impossible 
to wait that long — a floor has to be used, curing 
stops too soon, and the quality of the concrete 

Through a basic improvement m riie process of 

manufacturing Portland cement, 'Incor' has /ily 
times the curing efficiency of ordinary cement. That 
is to say, *Incor' combines with water five times as 
fast, so it only has to be kept wet one-fifth as long. 

Thus, in 2-4 hours an 'Incor' concrete floor is 
ready for heavy traffic, and in 4<S hours, 'Incor' 
concrete is as dense, durable and watertight as 
ordinarv concrete at the end of ten days. Any 
floor can be kept wet 4iS hours — but 10 days is 
another story! 

By producing thoroughlv cured concrete within 
the time limits imposed by practical necessity, 
*Incor* in the hands of skilled workmen produces 
longer-wearing heavy-duty floors. 

It costs money to cure concrete, by saving cS days' 
curing expense, *Incor' introduces a new factor of 
economy in floor construction. 

Finally, with 'Incor' a heavy-duty floor can be 
completely resurfaced over a single week-end, 
without costly interruption to business. This re- 
moves one of the biggest obstacles to adequate floor 
maintenance. There is no longer any sound reason 
for putting up with the waste and inconvenience of 
a worn-out floor, when a new and more durable 
floor-topping can be placed after the close of busi- 
ness Saturday — and be ready for heavy-duty serv- 
ict- first rhiiiu Mondav morninir. 


Digging Out 

In resurfacing an old floor, the surface should be 
removed and the concrete roughened with pick, 
air-drill or other mechanical device, in order to 
secure a good bond. When only part of a floor is to 
be repaired, suflficient concrete must be removed so 
that the surface of the new work will be level with 
the surrounding floor. This is done by digging out 
a depth equal to that of the top to be placed, 
usually about one inch. 

Sweeping and Washing 

The base is then carefully swept and washed. 
One operator successfully uses a portable pump de- 
veloping 250 to 400 pounds, delivering water 
through a 3^" nozzle. The pressure produces a 
high-velocity stream that thoroughly cleans all 
pockets in the base; the small diameter nozzle mini- 
mizes the quantity of water to be removed from 
the floor after cleaning. This water jet also removes 
all loose material from the base, which is then ready 
to receive the grout. Where high pressure is not 
available, extra care should be taken to wash and 
broom thoroughly. 



New Construction 

While the surface of the slab is still soft, it 
should be thoroughly roughened with a rake or 
steel broom. This removes scum and assures a good 
mechanical bond with the top when placed. The 
base should be kept wet until thoroughly cured— 
lo days with ordinary cement, 24 hours with 
'Incor.' Thorough curing of the base is necessary to 
avoid shrinkage cracks that may also afl^ect the top. 

If the top is applied monolithic with the base it 
should be laid within 45 minutes after the base is 
placed. As the top will draw any excess water out 


of the base, the total water content of base and top 
must be kept low enough to prevent the finishing 
operations from bringing fine material to the 

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Trimming the Edge 

On floor patches, care must be taken to get a 
strong, durable bond between the old wearing 
course and the newr. The edges of the chipped out 
area should be cut clean and vertical to full depth; 
the bottom should be roughly leveled so that it 
forms a right angle with the edge. If carelessly 
handled, the joint is usually the first part of the 
floor to break down in use. 

Setting Screeds 

Before placing the concrete, wooden strips or 
screeds are set in cement mortar at distances con- 
venient for straight-edging, say 8 to 10 feet. These 
strips are brought to grade by means of spirit-level, 
chalk-line or other method. A true, level floor de- 
pends upon the accuracy with which this work is 


between new and old work is important. Carelessly 
made joints will break down and widen under 
traffic. In extreme cases, a serious rut may develop. 
Photograph at left shows an improperly made joint 
between the floor slab and a section which was 
placed later, to close an elevator opening. Note how 
edges have broken down under traffic; surface 
cracks indicate inadequate curing. Photograph at 
right shows how such a joint, without maintenance, 
will develop into a serious depression. A properly 
made joint is illustrated in the centre picture. 

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Selecting Aggregates 

Care should be exercised in the selection of both 
fine and coarse aggregates. Sand should consist of 
hard, durable particles, all of which will pass 
through a J^" sieve and not more than 10 per cent 
through a 50-mesh sieve. Coarse particles should 

Clean, hard pea-gravel or crushed stone — free 
from dust, clay, loam or organic impurities, as well 
as soft, flat, or elongated particles — should be 
used. All material should pass through a sieve 
having H" openings and be retained on one having 
J4" openings. The maximum size of the largest 
particles should not exceed one-third of the thick- 
ness of the floor topping. 

Proportioning Materials 

A heavy-duty floor surface must be strong, 
dense, watertight. Watertightness is imperative; 
by preventing the penetration of water, dilute 
acids or other aggressive liquids, the life of the floor 
is greatly increased. Besides, watertight concrete 
is good concrete and therefore wear-resisting. 

Watertight concrete is obtained by mixing 
proper proportions of cement and water with 
good sand and stone; placing the concrete without 
segregation, and curing it thoroughly. 

The amount of water must be carefully con- 
trolled. For machine floating, use 31^ to 4 gallons 
of water to each 94r-pound bag of cement. For 
hand floating, use 4}4 to 4^ gallons. Reduce the 
quantity of added water by }4 gallon if sand is 
moist, or by 1 gallon if sand is wet. Measure water 
carefully — don't guess. 

With properly graded aggregate, proportions 
of from 1— 1— IH to 1 — 1—2 (cement, sand and 
coarse aggregate) give satisfactory results. These 
mixes usually produce workable concrete and allow 
finishing without excessive troweling. Here the 
greater workability of *Incor' Cement is helpful; 
*Incor' concrete is easier to place and compacts 
more readilx into a dense mass, because it is more 



Grouting the Base 

The base is thoroughly wetted. Then a .1 to 1 
cement-sand grout is brushed into the base. The 
grout provides a bond between the base and the 
new top. 

Spreading Concrete 

While the grout is still soft, the concrete is 
spread evenly with shovel or rake. The surface of 
the loosely-placed material is maintained above 
grade sufficiently to allow for compaction. 

Tamping and Rolling 

When deposited, the concrete has an open struc- 
ture, due to the limited quantity of water used in 
the mix. It is therefore necessary to compact the 
concrete thoroughly, in order to obtain the neces- 
sary density and to force the new material into the 
pockets in the base. Compacting is necessary in 
order to obtain a proper bond between base and 
top, as well as to secure a dense, durable surface. 

The loosely-spread concrete is compacted, first 
by tamping and then by a small, heavy roller. The 
roller illustrated weighs over five hundred pounds. 
Note the scraper which removes picked-up mate- 
rial from the surface of the roller. 

Tamping and rolling drive the topping down into 
the grouted base, helping to secure a bond between 
base and top. A good bond is necessary; the top- 
ping cannot stand up under use unless firmly 
'welded' to the base. Tamping and rolling also 
bond the vertical surfaces where new topping joins 
the old. 


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Cutting or Straight-edging 

Next the concrete is cut to grade by the sawing 
movement of a straight-edge resting upon wooden 
screeds which indicate the proper thickness of the 
topping. Any low spots are built up to grade by 
adding more concrete. 

After the floor has been struck to grade, the 
screeds are removed and the space left thereby is 
filled with concrete, which is tamped and rolled. 



Machine Finishing 

Machine finishing makes it possible to get a 
smooth surface with a very dry mix. A dry mix 
prevents separation of coarse from fine material, 
minimizes shrinkage, and keeps coarse material 
at the surface where it is needed to increase resis- 
tance to wear. With wet mixes, water and the 
fines from cement and sand tend to come to the 
surface in finishing; this may result in crazing, 
scaling, and dusting in the finished floor. 

The machine illustrated compacts and levels out 
the topping by means of a rotating steel disc. It 
brmgs to the surface only enough mortar to facili- 
tate steel troweling. This is only possible when the 
correct water content is used. Note that the 
operator's feet make no depression in the dry, 
compacted mass. 

Hand Finishing 

When finishing by hand instead of by machine, 
wooden or cork floats are used to fill up the hollows 
and iron out the humps left after cutting. This 
work should continue until a true, level surface is 
obtained. Care must be exercised not to draw any 
more fine material from the mass than is actually 
required to coat particles of coarse aggregate at 
the surface. 

Final Finishing or Troweling 

Fmishing with a steel trowel is the final step; it 
helps to make the surface dense, impervious and 
smooth. Four or five passes with the trowel are 
usually suflRcient. 

With a dry mix, which has been floated by ma- 
chme, there is practically no movement of finer 
materials to the surface during hand troweling. 
The float will draw too much fine material to the 
surface of a wet mix, impairing the wearing quality 
of the finished floor. 

If the methods outlined in this book are carefully 
followed, there will be no excess water. However, 
if too much water has been used, be careful not to 
use the steel trowel while any water sheen remains 
on the surface. 



You can easily put too much water on the inside 
of concrete, that is to say, in the mix; but you 
can't put too much water on the outside, that is 
to say, in curing it. 

The most effective method of curing is to flood 
the surface of the floor with water. If necessary, 
form low dikes of earth or other material, to pre- 
vent water from running off. Coverings of burlap, 
or similar material, kept thoroughly saturated 
with water, also may be used. 

As the greatest water loss through evaporation 
and absorption occurs during the first few hours, 
it is important to begin curing not more than six 
hours after placing the concrete. 

Why Curing Is Important 

The importance of curing is apparent when it 
is recalled that newly-placed concrete does not 
attain strength by '^drying out." In fact, the op- 
posite is true. Concrete hardens and attains 
strength by a chemical reaction between cement 
and water. This reaction begins when the water 
and cement are mixed, but continues only as long 

as water is kept in the concrete. If the slab is al- 
lowed to dry out before curing is well advanced, 
strength and durability are impaired. 

\ov concrete subjected to grueling wear, as in 
heavy-duty floors, 10 days' curing under water is 
necessary when ordinary Portland cement is used. 
But job conditions impose drastic limits on the 
length of curing time — a factory or warehouse floor 
simply cannot be kept out of use that long; a road 
or driveway must be opened to traffic; even on 
new buildings, plumbers, carpenters and electri- 
cians must use the floor. Because the floor has to 
be used, curing stops too soon — and the quality 
of the concrete suffers. 

How 'Incor' Solves the Problem 

Through a basic improvement in the process of 
manufacturing Portland cement, 'Incor' cures, 
that isy combines zvith zvater, five times as fast as 
ordinary cement. That is why an Tncor' floor — so 
far as strength is concerned — is ready to use in 24 

In fact, because it cures five times as eflRciently, 
Tncor' kept wet for only 24 hours has greater 
durability and watertightness than ordinary con- 
crete as cured on the average job. However, we 

A. Jt^ j 






recommend that heavy-duty floors made with 
'Incor* be kept wet for 48 hours — at which time the 
concrete is as thoroughly cured as ordinary cement 
at the end of 10 days. 

Any floor can be kept wet 48 hours — but 10 days 
is decidedly another story! By producing thorough- 
ly cured concrete in the limited time the floor can 
be kept wet, *Incor' in the hands of skilled work- 
men produces longer-lived floor surfaces. 

Used In Leading Industrial Plants 

Since it was first introduced eight years ago, the 
nation's leading industrial concerns have been 
turning to 'Incor* for the solution of the heavy- 
duty floor problem. To sum up the reasons: 

*Incor* produces concrete which is stronger, more 
watertight and longer wearing — because it cures 
thoroughly in the short time the floor can be kept 
wet. At the same time, it substantially reduces 
curing costs. 

In addition, *Incor* makes it possible to re-sur- 
face a floor without tying up business. A new 
*Incor' floor topping can be placed over a single 
week-end; the entire job — from digging out the 
old floor to the new topping, thoroughly cured and 
ready for service — is now completed between the 
close of business Saturday and opening time Mon- 
day morning. 

*Incor' prevents business dislocation for the 
same reason that it makes longer-wearing concrete 
— simply because it is a better Portland cement. 

WHEN WINTER COMES: Practice outlined in this 
book is based upon normal temperatures. In Winter, 
the greater curing efficiency of *Incor' minimizes 
the period of heat curing. Thus heating costs are 
reduced — new floor surfaces are placed and put In 
service on Summer schedules. For details, write for 
booklet entitled ** Winter Construction with *Incor** 
24-Hour Cement.'* ♦Reg u. s Pat Off. 




Busy floors like this wear out under heavy traffic. They have to be repaired. Yet, 
they cannot be kept out of service. *Incor' Cement solves the problem by produc- 
ing new floors over a week-end, without tying up business operations. And 'Incor' 
makes stronger, denser, more watertight concrete by curing thoroughly in 48 hours. 

..Rio de Janeiro 


jtar Cement Company Alabama l„dtonapolis 

Star cement Company '"O'-- "^ — „ cuy. Mo. 

.one Star Cement Company (Kansas) - ^^^ ^^^^^^^ 

Star cement Company ';;^-:Z:^::,^^.,^^ 
Star cement Company New York, Inc „„,h 

Star cement Company Pennsylvania '^^ J^^,^^ „^„,,„„ 

, star Cement Company Texas Norfolk 

. Star cement Company Virginia, Inc.... -^ ^.^^^ 

,„tine Portland Cement Company—- ^^ ^^^^^^^ 

ional Portland Cement Company (Bra..l) ^^^^^^ 

, Cuban Portland Cement Corporation. ;,„„.evideo 

,ftuay Portland Cement Company - 

Subtidiaries o/ 

,ternational Cement Corporation 

Printed in U. S. A.